Belarus's authoritarian president threatened to "wring the necks" of opponents preparing to take to the streets during tomorrow's elections, which he is widely expected to win with 70% of the vote.

Alexander Lukashenko, who has been accused of heavy-handed tactics in attempting to prevent a repeat of the "revolutions" that took place in Georgia and neighbouring Ukraine, said yesterday that his liberal opposition had "neither the brains, the strength or the resources to take over anything".

He added: "God forbid they should commit any sort of act in our country," he said. "We will wring their necks as one might a duck."

Victory should come easily for Mr Lukashenko, who is expected to win a third term making him Europe's longest serving leader. State television shows him in a land of plenty, riding high on economic stability and "independence" from an expansionist Nato to his west.

But amid the harmony lies great discord. "Lukashenko looks tired and worried despite him having the vote sewn up," said one senior western diplomat, who concedes he may enjoy between 25% and 50% of the electorate's support.

The burly former collective farm boss is emboldening his enemies more than he is keeping his friends.

In a week that saw dozens of opposition activists arrested and foreign election monitors turned away at the airport, the KGB - which retains its Soviet name - claimed that Georgian embassies in Lithuania and Ukraine were plotting to destabilise the vote.

Yesterday the Bush administration turned the screw on this "outpost of tyranny" by releasing a dossier detailing Mr Lukashenko's personal finances and Belarus's arms deals.

The EU and the US have accused Mr Lukashenko of denying free speech and controlling the media, warning that "targeted sanctions" may follow if, as expected, observers declare the election fraudulent. The EU is funding an "independent radio station" that on Thursday began broadcasting from Poland.

Even Mr Lukashenko's ally, Moscow, has been muted in its support, although it is keen to prevent a repeat of the "revolutions" that turned Ukraine and Georgia towards the west.

Russia's president, Vladimir Putin, who feels little personal warmth for his Belarussian counterpart, has kept silent about an election that would draw both western condemnation and embarrassment for him during Russia's G8 presidency.

Protesters, due to hit the streets at 8pm tomorrow dressed for a "denim revolution", have been warned they could be charged with terrorism, and face the death penalty. "Without fear to hold it together this place would fall apart," joked one taxi driver.

Alexander Milinkevich, the main opposition candidate, has been accused of trying to seize power through a foreign-funded coup. At least 50 of his activists were arrested last week.

"People are still very afraid, but we have politicised the country," Mr Milinkevich told the Guardian. "They are reacting to us."

Many analysts feel the only hope for change is from within the elite, anxious to avoid the pariah status a third Lukashenko term would bring.

The message from Minsk riot police to protesters yesterday was that they will be "forced to the ground".

But EU foreign policy chief Javier Solana warned of "strong international reaction" if violence were used on peaceful demonstrators.

Alexander Kozulin, another opposition candidate, was beaten by special forces officers when he tried to enter a hall where Mr Lukashenko was speaking. One of the assailants shot out the tyres of his car. Mr Kozulin was taken to a police station where he damaged a portrait of the president, for which he is now facing charges.

"Lukashenko is the destabilising factor. We have a fascist state here," Mr Kozulin said. "It is 'Lukashism'. His place in The Hague has been freed by Milosevic."